1. Field of Invention
The present disclosure relates to a system for creating pulses in wellbore fluid. More specifically, the present disclosure relates to a downhole telemetry system with a multi-ported valve.
2. Description of Prior Art
Information about a hydrocarbon producing formation are often obtained during operations conducted a borehole that intersects the formation. Typical wellbore operations that also involve gathering downhole information include measuring while drilling (MWD) and logging while drilling (LWD). The formation information generally includes downhole fluid pressure and/or temperature, and information about the formation, such as its resistivity, density, tool orientation and position, and porosity. The information obtained during MWD and LWD is usually communicated to surface via mud pulse telemetry in real time, where fluid flowing through a downhole string is intermittently metered in order to create pressure pulses in the fluid. During mud pulse telemetry, metering the fluid is done sequentially to generate discernible signals, represented by pressure variations in the fluid, that are thee carried by the fluid back to surface. The sensors on the surface (e.g., pressure sensors) will convert the pressure change in the mud system to electrical signals for further processing.
Some currently known mud pulsers use plungers or disk actuators for creating pressure pulses. The plunger type actuators blocks and released mud flow by a piston in the mud channel, and can be oriented vertically or horizontally. Disk actuators are made up of horizontally disposed disks that have axial openings. Rotating or oscillating the disks with respect to one another selectively moves the openings in and out of registration to intermittently block and allow flow across the disks, thereby introducing pressure pulses into the drilling fluid. A drawback to the use of plungers for creating mud pulses is the force required to move the plunger in and out of the way of its associated opening. The large force required to move the plungers limits the speed at which the plungers can operate, thereby limiting the data density that can be relayed uphole. Similarly, large shear forces between the rotating disks resists their respective rotational speed.